The show picks up one year later at Gina's wedding and we learn that Ryan and Max are in new relationships and Max has joined the FBI. Mike has spent the last year chasing Mark which is why he and Max broke up.
At the wedding, a waiter throws blood on Ryan. We later learn that the waiter is Andrew and he is not only one of Mark's followers, but also the one who picked him up at the end of season 2.
The other new villains are Kyle and Daisy. They kill another couple in their hotel room and leave the message "Ryan Hardy Lies" at the crime scene.
Ryan, Max, and Mike manage to track the waiter to an address and when they arrive, they find a second crime scene. This one is staged to mirror the scene when Max killed Luke. The message "Max Hardy Lies" is left at the scene. The team realizes Mark is the one behind the murders.
Mark now talks to himself as Luke and even eats dinner across from a mirror as if he's eating with his brother.
Ryan realizes Mark's next victim will be a doppelganger of his mother. They track Mark to a bar and Ryan arrests Andrew, but Mark has already kidnapped a woman and gotten away.
By the time Ryan, Max, and Mike arrive, Mark has killed the woman and staged the scene to look like the one when Mike killed Lilly Gray. The message left reads "While you lie, more die."